1. Field of the Invention
This invention relates to antireflectance coatings for sodium chloride and potassium chloride laser windows.
2. Description of the Prior Art
Laser systems utilize thin-film coatings to create high- and low-reflectance surfaces. The performance of these coatings in a particular laser system limits the power-handling capability of that system. Improvement in performance has been sought by investigating (1) design, (2) methods of deposition and (3) materials.
Insofar as materials are concerned, only a few have been carefully studied. Studies were made on Ge, MgF.sub.2, As.sub.2 S.sub.3, BaF.sub.2 and ZnS and reported in 1970. The results of these studies indicated that As.sub.2 S.sub.3 and BaF.sub.2 were the best choices as materials from which to fabricate multilayer antireflectance coatings for use at 10.6 .mu.m wavelengths. More recent studies stressed the use of the ThF.sub.4, BaF.sub.2, ZnS, ZnSe, As.sub.2 S.sub.3 and TlI. Very recently, lanthanide fluorides have been studied. Insofar as is known by the inventors, the materials NaF and As.sub.2 Se.sub.3 were never studied prior to tests leading to the present invention.